Resonance Structures

Question 0

Allylic

Answer 0

Atoms connected directly to vinylic positions.

Question 1

Vinylic

Answer 1

Carbon atoms double bonded to each other.

Question 2

5 patterns:

Allylic lone pair

Answer 2

Look for lone pair in an allylic position. Resonance structure can be solved with two arrows:
Lone pair to pi bond> pi bond to lone pair.
Move lone pair toward vinylic pi bond.

Question 3

5 patterns:

Allylic positive charge

Answer 3

Look for positive charge in Allylic position.
Only one curved arrow is needed.
If molecule contains two orore pi bonds, we can ‘push’ each double bond over one at a time.

Question 4

5 patterns:

Lone pair adjacent to a positive charge

Answer 4

Requires only one arrow.

Lone pair is pushed toward the positive charge.

Question 5

5 patterns:

Pi bond with two atoms of differing electronegativity

Answer 5

One arrow needed.

Push pi bond up onto electronegative atom to become a lone pair

Question 6

5 patterns:

Conjugated pi bonds enclosed in a ring.

Answer 6

3 arrows needed.

Push each pi bond over one position.

Question 7

3 questions about significance:

Answer 7

Acceptable number of charges (2 or fewer)?
Do all electronegative atoms have a full octet?
Are carbons with opposing charges avoided?